1. Field of the Invention
The present invention relates to a magnetic recording method for recording information by utilizing a change in magnetization, and to a disk device, adopting the magnetic recording method, used as an information storage device for a computer.
2. Description of the Related Art
The role of information storage devices played by disk devices including hard magnetic disk devices and optical disk devices is getting more and more important. There is a strong demand for high-performance disk devices.
In particular, it is most important to record information at a high density on a magnetic recording medium and read it from the magnetic recording medium. A magnetic film suitable for high-density recording and used to coat a recording medium is formed using a technique such as sputtering, and is provided in the form of a polymer of minute magnetic particles.
With the demand for higher-density information recording, finer magnetic particles are being used. Presumably, when the diameter of a magnetic particle is on the order of approximately 10 nm (currently, approximately 30 nm; 1 nm=10xe2x88x929 m), a state in which information can be stably recorded becomes difficult to maintain because of the influence of thermal agitation. For maintaining a stable information-recorded state, a magnetic material for recording, to which a large coercive force (Hc), that is 4 to 5000 Oe or two to three times higher than a coercive force applied to a conventionally employed magnetic material, must be applied, must be adopted for producing a magnetic film for a medium.
Using such a medium, the magnetic field required for recording information becomes very large (two to three times higher than Hc). A magnetic head formed with a normal magnetic material would have difficulty in recording information on the medium.
However, as far as a recording medium requiring a large coercive force (Hc) is concerned, a technique for recording information has not been devised. It is therefore uncertain whether or not a medium with a high recording density can be put to practical use.
The present invention attempts to solve the foregoing problems. An object of the present invention is to provide a magnetic recording method capable of recording information on a stable basis even when a magnetic material for recording to which a relatively large coercive force must be applied is used to record information, and to provide a disk device suitable for high-density magnetic recording by utilizing the magnetic recording method.
For solving the problems, according to the present invention, there is provided a magnetic recording method in which, when a magnetic head is used to record information on an information recording medium or read the information recorded on the information recording medium, the temperature of a portion of the information recording medium on or from which information is recorded or read is changed in order to record or read information.
Preferably, a recording medium having projections or grooves, which provide position information used to position a recording head of the magnetic head designed for recording information or a reading head thereof designed for reading information and formed therein in advance, is used as the information recording medium.
More preferably, the information recording medium is heated locally by laser light.
More preferably, a transparent or translucent magnetic material is used to produce the information recording medium.
More preferably, the magnetic material is formed with a laminate film having two or more layers.
More preferably, a material that is transparent relative to the wavelengths of laser light is used to produce a substrate for the information recording medium.
According to the present invention, there is provided a disk device comprising: an information recording medium on which information is recorded according to a change in magnetic field and then preserved; a magnetic head for recording information by applying a given magnetic field to the information recording medium, and reading the information recorded on the information recording medium; and a temperature changing mechanism for changing the temperature of a portion of the information recording medium on or from which information is recorded or read. The magnetic head is moved to the portion of the medium, in which a temperature change is produced by the temperature changing mechanism, in order to record or read information.
Preferably, according to the present invention, there is provided a disk device in which a recording medium having projections or grooves, which provide position information used to position a recording head of the magnetic read designed for recording information or a reading head thereof designed for reading information and formed therein in advance, is used as the information medium.
More preferably, according to the present invention, there is provided a disk device in which the temperature changing mechanism comprises an optical system including a laser. Laser light emanating from the laser is used to locally heat the information recording medium.
More preferably, according to the present invention, there is provided a disk device in which a transparent or translucent magnetic material is used to produce the information recording medium.
More preferably, according to the present invention, there is provided a disk device in which the magnetic material is formed with a laminate film having two or more layers.
More preferably, according to the present invention, there is provided a disk device in which a material that is transparent relative to the wavelengths of laser light is used to produce a substrate for the information recording medium.
More preferably, according to the present invention, there is provided a disk device in which at least one of the recording head of the magnetic head designed for recording information and the reading head thereof designed for reading information is moved while being interlocked with the temperature changing mechanism.
In detail, according to the present invention, there are provided a magnetic recording method and disk device in which a laser or the like is used to irradiate light for heating, and to thus reduce a coercive force (Hc), which must be applied to a magnetic film used to produce a high-density recording medium, to a the level permitting reliable recording. In general, when a magnetic substance is heated, a coercive force Hc that must be applied to the magnetic substance for recording tends to decrease. When the magnetic substance is heated to the Curie temperature, the coercive force Hc becomes zero (Hc=0). The limit temperature of CoCrPt used for normal magnetic recording is on the order of approximately 500xc2x0 K.
A recording head moves according to a position to which laser light is irradiated, whereby a heated area becomes coincident with a recorded area to which a magnetic field is applied. During reading, since the temperature of a magnetic substance is equal to the room temperature, the magnetic substance is free from thermal agitation. A stable information-recorded state can therefore be attained.
According to the present invention, there is provided an information recording method and disk device suitable for high-density recording and capable of preserving recording information on a stable basis. Furthermore, there is provided an information recording method and disk device capable of providing servo information suitable for high-density recording.